Method for processing plant protein

ABSTRACT

There is provided an improved process for the separation and purification of plant proteins by initially separating the chloroplastic and cytoplasmic protein fractions, further treating the chloroplastic protein fraction enzymatically and extracting out other unfavorable substances. The resulting chloroplastic fraction has favorable properties close to that of the cytoplasmic fraction and is thus valuable for human consumption.

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation of Ser. No. 790,248 filed on Apr. 25, 1977, nowabandoned.

The invention relates to a method of processing green plant protein,especially to an improved method for separating and purifying proteincomponents from green plants.

In a broad sense all green plants having photosynthetic activity areconsidered suitable for processing according to the invention. Theprotein content thereof after isolation and, in given cases, afterconcentration can be utilized on a commercial scale.

The difficulty in recovery of green plant protein is in the separationof fractions having different value from accompanying substances and theadaptation of the valuable fractions for human or animal consumption.There is therefore a need to provide more economical methods on anindustrial scale to improve the separation of green plant proteins.

It is known that the pressed juice obtained via pressing of green plantscontains protein fractions coagulable under heat treatment and havingdifferent values. In the framework of these methods a separation of thechloroplastic and more valuable cytoplasmic protein fractions representsa rather complicated task. An improvement in the separation, however, isof decisive importance because the cytoplasmic protein fraction containsthe most valuable protein fractions inherent in the plant material.These are not bound to chloroplastids and contain only low amounts oflipids and mineral accompanying substances. The cytoplasmic proteinfraction is therefore suitable for use in human consumption because ofits lack of odorous and aromatic substances which provide for a moreappealing and therefore edible fraction. A main task in the processingof green plant protein is to increase the ratio of cytoplasm proteinfraction to the amount of the protein available.

The chloroplastic protein fraction contains the major part of theminerals present in the accompanying substances, the major part of thelipid content, and practically all of the lipid soluble pigmentsubstances of which chlorophyll, xantophyll and beta-carotene are themost significant. The processing of the latter protein fractionrepresents an independent technical task in the working up of the greenplant protein. On the one hand, the separation of the accompanyingsubstances from the protein which are present in the chloroplasticprotein fraction should be solved in order to increase the proteincontent and to improve the quality. On the other hand, the processing ofthe lipid-soluble dye substances, the pigments for foddering purposes,should be elaborated. The importance of pigment substances has recentlyincreased in closed livestock farming because the pigments areindispensable components in breeding certain kinds of animals in orderto bring about their natural color.

The complicated process of fractionating by heat treatment for theseparation of chloroplastic and cytoplasmic protein fractions has beensuggested. It is, however, disadvantageous because the two fractionshaving different value but physically very analogous properties cannotbe separated sharply. In the course of the heat treatment a part of theprotein precipitate is damaged and the pigments and other accompanyingsubstances in chloroplast fraction which detrimentally influence theproperties necessary for human consumption, cannot be removed. Differentorganic solvents or a combination thereof have been proposed for theextraction of the pigments present in the chloroplastic proteinfraction. The hitherto known processes, however, can be realized only ona laboratory scale.

An object of the present invention is to increase the amount of thecytoplasmic protein fraction which can be obtained on processing greenplant protein from the pressed juice via pressing; a treatment of thechloroplastic protein fraction to improve the separation of pigmentsubstances, and an improvement in the efficiency of the extraction, animprovement of the properties of the chloroplastic protein fractionwhich render the fraction more appealable for humanconsumption--after--fraction.

Summing up an increase in the ratio of the green plant protein insidethe total protein mass having a quality identical to the cytoplasmicprotein fraction on processing a given plant protein is a main object ofthe invention. A further important object is the processing of thepigment substances which can be obtained from the chloroplastic fractionvia solvent extraction into a pigment concentrate suitable forindustrial purposes.

According to the present invention for processing green plant protein,especially for the improvement of separation and purification ofobtainable protein substances the following measures should be taken:

(a) the chloroplastic protein fraction is flocculated in the presence ofinorganic agents promoting the flocculation at a temperature below 50°C. from the pressed juice which is obtained via pressing of the greenplant material and is separated preferably in two steps;

(b) the extent of the heat treatment necessary to coagulate the proteinand therewith effect the separation of the chloroplastic and cytoplasmicprotein fractions is controlled by measuring the pigments concentrationof the juice flowing off the separator with light absorption method;

(c) the separated chloroplastic protein fraction is treated in anaqueous suspension with a protease enzyme, if desired, after a treatmentwith a polar solvent;

(d) the chloroplastic protein fraction treated with the enzyme isextracted in a wet state with a polar solvent or a mixture of saidsolvents, the solvent is recirculated after regeneration into theprocess;

(e) the extracted pigment and lipoid concentrate is utilized aftermixing it with an inert carrier or a carrier having a stabilizingeffect;

(f) after separation of the chloroplastic protein fraction the remainingpressed juice containing the cytoplasmic protein fraction is treated tocoagulate the protein at about 80° C. or the precipitation of the iscarried out by treating the juice with a solvent;

(g) the coagulated proteins precipitated are utilized separately ormixed with each other after drying as animal fodder or for humannourishment.

The juice obtained by pressing the plant material is either heated tocertain temperatures or treated with inorganic flocculation agents, suchas the calcium, aluminum and iron salts or the hydroxides respectively,which are applied based on the green plant juice in an amount notexceeding 70 ppm or preferably based on the dry matter content of thepressed juice in an amount not exceeding 800 ppm to coagulate thechloroplastic protein fraction. The coagulated chloroplastic proteinfraction is separated preferably in separators coupled in series. Thefirst stage of the two-step-process is carried out in a decanter typeseparator, the second step in a self-discharging disc separator. Inaddition, there is a possibility to backfeed the separated dilute sludgeinto the first stage thereby ensuring that a sludge discharge shouldoccur only in the first stage. Completing the separation of thechloroplastic protein fraction in two steps the chloroplyll content ofthe juice flowing off is decreased to a negligible extent by measuringthe light absorption value of the juice with a photometer inserted inthe take-off pipeline of the second separation stage. Thus thetime-period necessary for the heat treatment can be adjusted. Theseparated chloroplastic protein fraction is treated in an aqueoussuspension in an alkaline or acidic medium with a proteolytic enzyme. Incase the pigment fraction is isolated the protein precipitate is treatedin a mildly alkaline medium with an alkaline protease which is aprotease prepared with fermentation from a fungus or a bacterium.Another variation of this method is that the precipitated chloroplasticprotein reaction is extracted at once, in still wet state, with polarsolvents and after extraction is treated in a mildly acidic medium withpepsine or papaine, or with a fungus bacterial protease functioning inacidic medium. The enzymatic treatment is realized in a suspensionhaving a dry matter content of about 15-25% by weight and is continueduntil at most 5% by weight of the protein value present is decomposed.The solvent applied in the extraction is methanol, ethanol, propanol,isopropanol, acetone, methyl ethyl ketone or dimethyl sulfoxide. Afterseparation of the lipid soluble pigment fraction with extraction, thesolvent is regenerated from the extraction liquid through an atmosphericdistillation, as a rule in the presence of an antioxidant, the remainingpigment concentrate is in turn dried, if desired, after mixing with anedible consumable carrier. It is important to start the extractionalways with a mixture of solvent and water, the starting ratio of waterand solvent being at least 80:20% by volume. This ratio is adjusted bycontinuously increasing the solvent ratio and decreasing the watercontent.

After separating the chloroplastic protein fraction the remained pressedjuice is treated at about 80° C. to coagulate the remaining proteins.The coagulation can be carried out by treating the mother liquor, with asolvent. The mother liquor, however, is evaporated to 1/3 to 1/4 part ofits original volume prior to solvent coagulation.

The extracted or enzymatically treated extracted chloroplastic proteinwith respect to its edible properties. comes near to the quality of thecytoplasmic protein fraction consequently, if desired, it can beutilized in admixture with a cytoplasmic protein fraction in thepractice.

It has been recognized that the coagulation of the chloroplastic proteinfraction can be improved and the applied temperature can be lowered byusing flocculation agents. This makes possible the separation of the twoprotein fractions to a sharper extent and the chloroplastic proteinfraction coagulated at a lower temperature is more suitable forconcentration and for removing the accompanying substances. The normallydifficult extraction of pigment substances can be made easier if theprecipitated chloroplastic protein fraction is treated enzymatically.The enzymatic treatment modifies the structure of the composite proteinand the treated precipitate still in a wet state can be extracted moreeasily and with a smaller solvent quantity than otherwise. Thecoagulation of the chloroplastic protein fraction at a lower temperaturecan be considered surprising because the applied flocculation agentsexert their effect selectively and the ratio of the cytoplasmic proteinfraction inside the total quantity of the protein mass can be increasedthereby. According to the invention a coagulation of the cytoplasmicprotein fraction can be hindered at a lower temperature. The favourableeffect, however, is due not only to the action of the flocculationagents but to the fact that the separation process can be followedaccording to the invention by measuring the pigment concentration in aphysical way by means of the light extinction of the juice flowing offthe separator.

According to our experience on processing the same green plant asubstantial shift in favour of one protein fraction can be attainedwithin narrow temperature limits, for example, applying the samecoagulation time, e.g. a pressed juice of Spinacea oleacea green plantwith a dry matter content amounting to 8% by weight is heat treated at48° C. and 54° C. for 120 seconds. The relative weight percent of thechloroplastic protein fraction based on the total amount of the proteinrecovered via coagulation is at 48° C. 75.3% by weight, at 53° C.already 80.0%. by weight, and, naturally, by an extent proportional tothese amounts the ratio of the more valuable cytoplasmic proteinfraction is decreased. These experimental data show therefore that anincrease of the cytoplasmic protein fraction depends on the temperatureused on coagulating the chloroplastic protein fraction. At 46° C., thechloroplastic fraction cannot be precipitated to a whole extenttherefore the flocculating agents according to the invention are usedfor promoting the precipitation.

Other experimental data prove that on processing other green plantmaterial, as Spinacea, if the coagulation is carried out at 46° C. thenabout 80% by weight of the total protein amounted is precipitated inform of the chloroplastic protein fraction. Carrying out, however, thecoagulation in the presence of a 0.2% by weight aqueous AlCl₃ and/orcalcium hydroxide solution, the amount of the chloroplastic proteinfraction is decreased from 80.0% by weight to 74.0 and 64.0% by weightrespectively, that is, the amount of the more valuable cytoplasmicprotein fraction can be increased at the expense of the chloroplasticfraction by coagulating this fraction at a lower temperature.

Further important result is that on treating the chloroplastic proteinfraction enzymatically the dye substances characterstic to this fractionand other components influencing unfavourably the edible properties ofthe protein can be removed in a more complete manner. Thus the qualityof the chloroplastic protein fraction comes near to the favourableproperties of the cytoplasmic fraction after the enzymatic treatment andextraction.

The process of the invention is illustrated further on basis of thefollowing Examples:

EXAMPLE 1

1000 kg of alfalfa (Medicago sativa) at the beginning of the green budstate having 28% by weight of dry matter and 4.8% by weight proteincontent was disintegrated. After disintegration the ground product waspressed in a continuous screw press at first under a pressure notexceeding 15 atm. thereafter at 80 atm. As a result of the pressing 800kg of pressed juice with 1.0 weight % dry matter content was obtainedwhich had a crude protein content based on dry matter amounting to 36%.

600 ppm calcium hydroxide per kg dry matter content of pressed juice wasadded in form of a saturated aqueous solution to the juice and washeated to 46° C. The heating was effected by injecting steam with 2 atmpressure. The injection of steam was controlled by the temperature ofthe juice removed from the system. The chloroplastic protein precipitatewas separated quantitatively and a fluffy precipitate was formed. Theobtained sludge was separated in two steps. In the first step the sludgewas conducted in a screw separator of decanter type where the bulk ofthe coagulated protein fraction was separated. The juice leaving theseparator containing 0.5-1.0 volume % dilute sludge was added directlyinto a self discharging disc separator which is the second apparatus ofthe separation unit. The second juice is led off the separator underpressure in a way that the light extinction value of the clear juiceleaving the separator was measured in 1:1 dilution with a photometer at600 nm wavelength visible light with the aid of cuvettes of 1 cm size.The discharge time periods of the separator was controlled in a mannerthat between two discharge periods the sludge was filled not more than50% of its whole volume with juice. In the pipeline of the cleared juicecontaining chlorophyll an inserted photometer measures the reduction ofthe light intensity. In the presence of chlorophyll, therefore, thephotocurrent intensifies and at an extinction value higher than 0.05 (atwavelength 600 nm) this photometric regulation decreases the efficiencyof the feeding pump of the separator unit and simultaneously a forceddischarge takes place in the second separator. Thus the separation ofthe chloroplastic protein fraction can be controlled accurately.

The dilute sludge obtained periodically in the second separator has anincreased mother liquor content therefore it is recirculated into thebuffer tank which is placed before the feeding pump of the separatorunit. Sludge is removed only from the first decanter separator with acontrolled water content. The sludge obtained from the first separatoris adjusted to a dry matter content of 30.0 to 35.0 % whereas the drymatter content of the sludge obtained from the disc separator was 10 to15% by weight.

The chloroplastic protein fraction separated in the above manner amountsto 142 kg with a 30% by weight dry matter content. 45.0 mg of butylhydroxy anisole is added to each dry matter kg of the chloroplasticprotein fraction and after homogenization the obtained product is driedin a flash type drying apparatus, inlet air temperature 250°-280° C. andoutlet air temperature 105°-110° C.

The weight of the dried product amounts to 45 kg and had a followingcomposition:

    ______________________________________                                        water                  6%                                                     crude protein         55%                                                     crude lipids           4%                                                     minerals              12%                                                     nitrogen free extract 23%                                                     beta carotene         800 mg/kg                                               xantophyll            1800 mg/kg                                              ______________________________________                                    

After the separation of the chloroplastic protein fraction the obtainedpurified juice was heated with direct steam injection (2 atm) to 80° C.and the coagulated cytoplasmic protein fraction is separated from thejuice in an apparatus identical with the separator for chloroplasticprotein fraction. The amount of the protein precipitate in wet stateseparated in two steps amounts to 45 kg, had a yellowish white colourand a dry matter content of about 30% by weight. The drying was effectedin a flash drier apparatus inlet air temperature 220° C., outlet airtemperature 105° C. The formed 14.5 kg of cytoplasmic protein fractionhad a following composition:

    ______________________________________                                        water                   7%                                                    crude protein           65%                                                   crude lipids            0.4%                                                  minerals                3.5%                                                  nitrogen free extract   24.1%                                                 chlorophyll, beta-                                                            carotene and xantophyll --                                                    ______________________________________                                    

Alternatively the separation can be carried out in one step in adecanter separator. The yield of the cytoplasmic protein fraction isthen decreased.

The utilization of the chloroplastic protein fraction is advantageouse.g. in the foddering of egg-laying poultry where the protein demand islimited and thus a complete substitution of carotenoid pigments ispossible. The cytoplasmic protein fraction is suitable without anylimitation to substitute optional protein carrier. After refinement,utilization in human nourishment is possible as well.

After separation of the chloroplastic and cytoplasmic proteinfractions--the weight of the condensed steam included--690 kg of motherliquor is formed. This was evaporated in a multistage vacuum evaporatoruntil a dry matter content of about 50% by weight of the residue andthis concentrate can be mixed in a proper proportion to the fibrouspresscake prior to drying thereof.

EXAMPLE 2

100 kg of alfalfa was processed according to Example 1. Thechloroplastic and cytoplasmic protein fractions were separated.

The green sludge isolated at the first separator of the chloroplasticprotein fraction separation is contacted in a stirring apparatus coupledto the decanter with a solvent. A fivefold amount (220 kg) of acetoneand 25.0 mg/kg dry matter butyl hydroxy toluene is added to the sludgebased on its dry matter content in a ratio proportional to its formationrate. The wet sludge is stirred for 15 minutes with solvent, thereafterin the decanting separator the sludge was isolated. The extractionliquid amounting to 265 kg is conducted to a tank and the residue freefrom solvent amounting to 100 kg was suspended in 200 liter of water andthe pH value thereof was adjusted to 1.8 and heated to 37° C. 1 g ofcrystalline pepsine was added to the mixture and treated therewith for 3hours. Thereafter the sludge was separated in a decanter separator andthe mother liquor, in a nearly neutralized state was intermixed withdilute juice to be vacuum evaporated. 90 kg of sludge was extracted with2×150 kg of acetone. After the extractions took place the solvent wasseparated and after regeneration was recirculated into the process. Theextraction residue was washed free from the solvent and dried in a flashdrier apparatus air inlet temperature 220° C. and air outlet temperature105° C.

The product weighing 31 kg is pale brownish-yellow with the followingcomposition:

    ______________________________________                                        water                  7%                                                     crude protein          70%                                                    minerals               6.0%                                                   total lipids           1.5%                                                   nitrogen free extract  15.5%                                                  ______________________________________                                    

265 kg of extraction liquid is conducted into a distilling apparatus and2.0 g butyl hydroxy toluene is added based on 10 kg of dry mattercontent. The solvent was distilled at atmospheric pressure and thusregenerated. The regenerated acetone was recirculated into theextraction step. 25 kg of distillation residue was adjusted with sodiumcarbonate to 7.5 pH value and was mixed in a homogenizing apparatus with5 kg of dextrine, 0.1 kg of sodium alginate and 0.9 kg of gelatinecontaining solution.

The homogenized mixture was dried in a spray drier apparatus furnishedwith a spray nozzle, air inlet temperature 200° C. and air outlettemperature 105° C. The composition of the obtained product weighing 14kg was the following:

    ______________________________________                                        water                  6%                                                     crude protein        16.5%                                                    minerals             22.0%                                                    beta-carotene        2500 mg/kg                                               xantophyll           4000 mg/kg                                               ______________________________________                                    

After separation of the cytoplasmic protein fraction the obtained motherliquor was processed according to Example 1.

The extracted chloroplastic protein fraction is suitable to substitutein animal foddering with an optional protein carrier in any quantity andusing in foddering optional animal species.

The cytoplasmic protein fraction can be utilized as well withoutlimitation as a substitute for any protein carrier for human nourishingpurposes. The chloroplastic protein concentrate prepared by enzymatichydrolysis combined with extraction can be dried together with thecytoplasmic protein fraction and the two fractions can be used incombination. The pigment concentrate is suitable for substitutingcarotenoid pigments in broiler and egg-layer poultry fodder and can beemployed independently from the chloroplastic protein fraction in animalbreeding.

EXAMPLE 3

1000 kg of Amaranthus mantegazzianus having a dry matter contentamounting to 18.0% by weight and a crude protein content of 3.9%.

The chloroplastic protein fraction was precipitated according toExample 1. 47 kg of wet sludge was diluted with water to 100 kg totalweight. The temperature of the mixture was adjusted to 40° C. and the pHvalue thereof with sodium hydroxide to 7.8. 32 g of a suspension of analkaline protease enzyme having an Anson-activity of 4-5 was added tothe mixture and mixed for 30 minutes. After the protease treatment thepH value was adjusted with a mineral acid to 4.5 and the mixture wasseparated. As a result of the separation 42 kg of sludge and 60 kg ofmother liquor was obtained, the latter being processed according toExample 1.

The sludge was extracted three times with 100 kg of isopropanol. Theextraction liquids obtained in each extraction step were united, thesolvent was distilled off and recirculated into the process. Thedistillation residue was processed according to Example 2, as additive 2kg of dextrine, 0.1 kg of sodium alginate and 0.5 kg of gelatine wereemployed dissolved in a solution. The obtained product amounted to 8 kgand contained 1600 mg/kg of beta-carotene and 3500 mg/kg of xantophyll.

The extracted residue was united with the cytoplasmic protein fraction.This fraction was precipitated by means of treating it with a solvent.

The separated juice obtained after removing of the chloroplastic proteinfraction was evaporated in a vacuum evaporator until 30% by weight drymatter content and the concentrate thus obtained weighing 100 kg wasadded together with the extracted chloroplastic protein fraction into150 kg of isopropanol and stirred for an hour. The mixture wasthereafter separated, washed twice with water and the solvent andaqueous solvent were distilled at atmospheric pressure. The regeneratedsolvent was backfed into the process. The protein precipitate washedwith water free from solvent and was dried. The weight of the proteinconcentrate was 27 kg, with the following composition:

    ______________________________________                                        water                   6%                                                    crude protein           75%                                                   minerals                6%                                                    crude lipids            0.2%                                                  beta-carotene, xantophyll                                                                             --                                                    ______________________________________                                    

EXAMPLE 4

The preparation steps of the pigment concentrate were combined to obtaina product suitable to intermix it with the usual fodders and to obtain aproduct having satisfactory shelf life. The carriers of the pigmentconcentrate were selected and the drying of the suspension prepared withthese carriers and the pigments was controlled in a manner that thedried endproduct should be free-flowable with a proper sizedistribution. In the course of the preparation of the concentrate suchmeasures were carried out that the surface of the prepared granulesshould be covered with a gastight material layer that is a product in aquasi-capsulated state was prepared. This gastight layer prevents thepenetration of the oxygen into the body of the product and ensures andincreases protection in addition to the use of an antioxidant.

The proper additives satisfying the above requirements are dextrine,gelatine, sodium caseinate and sodium alginate. Using these additivesthe pigment concentrate can be obtained in a quasi-capsulated form.Another advantage of these additives is that they form without vacuumevaporation a sludge having proper viscosity which can be dried into aproduct having a preferable size distribution by means of a spray drierfurnished with a spray nozzle or by means of a centrifugal spray drier.

The sludge prepared for spray drying is adjusted to a dry matter contentamounting to 30-40% by weight. The viscosity of the suspension obtainedis about 28°-32° E (Engler Grade) (at 40° C.). This suspension obtainedwas dried with a spray drier furnished with a single or two nozzles, aninert gas was used for spray drying having a pressure of 2.0-2.5 atm. Incase a centrifugal spray drier is used then the inlet air temperaturewas 210°-230° C. and the outlet temperature 100°-105° C.

The size distribution of the dried product was that it passed in itsbulk through a sieve having a 0.2-0.35 aperture size. The pigmentconcentrate is stable, stored at room temperature far more then a yearless than 10% by weight of its original carotenoid pigment content waslost.

What we claim is:
 1. A process for the separation and purification ofplant proteins from the pressed juice of green plants comprising(a)coagulating a chloroplastic protein fraction in form of a green sludgefrom said juice at a temperature below 50° C. in the presence of aninorganic flocculating agent; (b) separating said green sludge from aremaining juice and subjecting the sludge in an aqueous suspension to aprotease enzyme until about 5% by weight of the protein components aredegraded; (c) extracting said sludge after enzymatic treatment with atleast one polar solvent such that the water to solvent ratio is at least80:20 to remove pigments and lipids from protein; (d) isolating anextracted pigment and a lipid concentrate by distilling off the solventand drying the residue, and (e) isolating a cytoplasmic protein fractionby coagulating the remaining juice from step (b) at a temperature ofabout 80° C., separating and drying the protein precipitate.
 2. Theprocess of claim 1 wherein the green sludge is in an aqueous suspensionhaving 15-25% by weight dry matter content in an acidic or alkalinemedium with said protease enzyme.
 3. The process of claim 1 wherein theprotease enzyme used in an acidic medium is selected from the groupconsisting of pepsin, papain and a proteolytic enzyme having fungal orbacterial origin.
 4. The process of claim 1 wherein the protease enzymeused in a medium of pH 7.5-8.0 is trypsin or a protease enzyme which isderived from a fungus or bacterium.
 5. A process for the separation andpurification of plant proteins from the pressed juice of green plantscomprising(a) coagulating a chloroplastic protein fraction in form of agreen sludge from said juice at a temperature below 50° C. in thepresence of an inorganic flocculating agent; (b) separating the greensludge from a remaining juice and extracting said separated sludge withat least one polar solvent; (c) subjecting the extracted sludge in anaqueous suspension with a protease enzyme until about 5% by weight ofthe protein components are degraded; (d) extracting further said sludgeafter enzymatic treatment with at least one polar solvent such that thewater to solvent ratio is at least 80:20; (e) isolating the extractingpigment and lipid concentrate by distilling off the extraction liquidand drying the residue, and (f) isolating a cytoplasmic protein fractionby coagulating the remaining juice from step (b) at a temperature ofabout 80° C., separating and drying the protein precipitate.
 6. Theprocess of claim 5 wherein the extraction of the enzymatically treatedsludge is carried out with water-solvent mixture having a water-solventratio corresponding to about 80:20 by volume and thereafter increasingthe solvent and decreasing the water content of the extracting solvent,respectively.
 7. The process of claim 5 wherein the polar solvent usedin the course of the extractions is selected from the group consistingof methanol, ethanol, propanol, isopropanol, acetone, methylethylketone,dimethylsulfoxide and mixtures thereof.
 8. A process for the separationand purification of plant proteins from the pressed juice of greenplants comprising(a) coagulating a chloroplastic protein fraction inform of a green sludge from said juice at a temperature below 50° C. inthe presence of an inorganic flocculating agent; (b) separating saidgreen sludge from a remaining juice first in a decanter and then in aself-discharging disc separator; (c) controlling the time periodnecessary for heat treating the juice in step (a) by measuring thepigment concentration of the liquid phase flowing off by means ofmeasuring the light absorption value thereof; (d) extracting saidseparated sludge from step (b) with at least one polar solvent; (e)subjecting said extracted sludge in an aqueous suspension with aprotease enzyme until about 5% by weight of the protein components aredegraded. (f) extracting said sludge after enzymatic treatment with atleast one polar solvent such that the water to solvent ratio is at least80:20; (g) isolating an extracted pigment and lipid concentrate bydistilling off the extraction liquid and drying the residue, and (h)isolating a cytoplasmic protein fraction by coagulating the remainingjuice from step (b) at a temperature of about 80° C., separating anddrying the protein precipitate.
 9. The process of claim 8 wherein aninorganic flocculating agent is selected from the group consisting ofwater-soluble calcium-, aluminium- and iron salts or hydroxides based onthe green plant juice in an amount not exceeding 70 ppm and based on thedry matter content of the plant juice in an amount not exceeding 800 ppmper kg of dry matter.
 10. The process of claim 8 wherein thechloroplastic protein fraction is coagulated in form of a green sludgeat 46°-48° C.